I took the brake arm from a coaster brake hub that we disassembled for a cargo bed and bent it in the vice put a 3/8″ hole in it and dropped a bolt through it. Done. Simple and effective. The rod end joint is about $6.00, available and salvageable if you have an ATV shop near by. This is just bolted in to the handle of the tongue of the trailer in such a way as to allow it to rotate freely.
This prototype is complete. We have several trailers started that will be ready for delivery in the coming weeks. We will continue development of the trailers for the next couple months. While building the first 2 requested carts. One will be for Stewart, a mobile bike shop of course, and the other for a local urban farmer, as a farm to market cart.